Pipette



g- 1965 v. MORRILL, JR 3,200,650

PIPETTE Filed Nov. 14, 1962 2 Sheets-Sheet 1 INVENTOR. 14496447 414F244, :12

Aug. 17, 1965 v. MORRILL, JR 3,200,650

PIPETTE Filed Nov. 14, 1962 2 Sheets-Sheet 2 FIG. 5 j

I N VEN TOR. 406/144 Aid/FEM. L, :7!

1:, JM M14.

United States Patent 3,200,650 PHPETTE Vaughan Merrill, Jr., 26 S. Spoede Road, Creve oeur 41, Mo. Filed Nov. 14, 1962, Ser. No. 237,493 2 Claims. (Cl. 73-42533) 'level. Thereupon diluent in proper ratio to the blood volume is drawn into the pipette; the height of the entire column then registering with a predetermined mark applied to the exterior of the assembly.

The column of whole blood should be such as to completely fill the capillary tube portion of the pipette. T0

confirm that this is the case, the technician will ordinarily elevate the pipette and look through it to see that the capillary tube bore is completely filled. Due to the fact that this tube portion is connected to the bulb by fusing the parts together a light refracting zone will exist adjacent the upper end of the capillary tube. This zone makes observation difiicult.

By means of the present teachings, a pipette is provided which in effect eliminates this zone and provides in lieu thereof a clear window portion through which the interior of the pipette may be readily viewed so that the technician will have no difficulty in determining whether the height of the whole blood column is such that it com pletely fills the capillary bore.

Also, other zones of the pipette assembly will be free of light refracting characteristics so that the effort necessary to determine that diluent in precise ratio to the volume of blood has been drawn into the pipettes is reduced.

An additional object is that of designing a pipette which may be manufactured at minimum expense and in large quantities to in each instance furnish a precision instrument upon which a physician may fully rely.

With these and other objects in mind reference is had to the attached sheet of drawings illustrating one practical embodiment of the invention and in which:

FIG. 1 is a side elevation of a pipette;

FIG. 2 is a sectional side view thereof;

FIG. 3 is a fragmentary view of the zone of merger between the capillary tube and mixing chamber of the unit;

FIG. 4 is a sectional side view of that zone; and

FIGS. 5, 6 and 7 are partially diagrammatic, longitudina-l sectional views illustrating successive steps in the production of a pipette having a clear window portion between the capillary and the enlarged bulb in accordance with the present invention.

In these views the numeral indicates the capillary tube portion of the pipette and 6 the enlarged bulb thereof providing a mixing chamber, extends from this chamber. Tube 5 is formed with a bore 8 of such small diameter that a surface tension effect is achieved under which with the tube disposed in an inclined plane and its lower end immersed in blood, that blood will rise to fill the bore 8. In view of the fact that the capacity of that bore is predetermined, the volume of blood will be precisely known.

Contrary to conventional construction in which the An aspirating tube 7 inner end of the bore ordinarily merges into the interior of the mixing chamber, a Well portion 9 is provided at this zone and has a flat base surface extending at right angles to the axis of bore 8. In accordance with conventional practice, a mixing head it may be disposed within the chamber defined by bulb 6. Opposed to bore 8 and at the rear of the mixing chamber is the bore 11 of aspirating tube 7. Upon the surface of this tube a mark 12 is provided. This defines the upper end of the liquid column which should be established within the pipette in order to provide a proper dilution ratio between the blood and diluent. That ratio will correspond to a determination involving a white cell count or a red cell count.

As indicated above, the base of walls 9 is flat and preferably disposed at right angles to the axis of the capillary bore. In addition, the side walls are free from retracting effect and stresses normally resulting from fusing two pieces of glass together. I accomplish this result by forming the pipette in one piece in any suitable manner, as by shrinking a tubular glass blank under heat and vacuum as, for instance, in the manner taught in my co-pending applications for United States Letters Patent, Serial No. 733,794, filed May 5, 1958 now Patent 3,091,104 and Serial No. 845,971 filed Oct. 12, 1959 now Patent 3,091,105. Thus, a unitary pipette, is provided having a well portion formed in the zone between the capillary and enlarged bulb with the well having a flat base portion and with the glass surrounding the well being free from stresses and retracting effect.

Accordingly, a window is in effect included in the pipette adjacent the zone of merger between the capillary tube and mixing chamber. In other words, this area will be free of the refracting effect which ordinarily exists K at this zone due to the coupling of the parts as a final step no difficulty in determining that bore 8 has been completely filled to thus provide a proper volume of blood for 7 cell determination.

In FIGS. 5, 6 and 7, I have illustrated a partially diagrammatic logitudinal section, successive steps which may be employed in making a pipette of this type, in accordance with the teachings of my two above-identified patent applications. Thus, I have shown a tubular glass blank, larger in diameter than the enlarged bulb portion of the pipette. The tubular glass blank is assembled around a hollow tubular mandrel 16 and is suitably supported at opposite ends by a headstock and tailstock (not shown). The right hand end of the mandrel 16 is of smaller diameter than the left hand end 16" and a shoulder is provided at the juncture between the mandrel sections of different diameter. The mandrel section 16' is of a suitable size to provide a capillary bore 8 in the pipette of the desired diameter and the mandrel section 16 is of the proper size to provide a bore 11 in the aspirating section of desired diameter.

In order to provide the desired bulb portion of the pipette as taught in my above-identified application, I assemble a pair of shell sections 18 and 20 around the mandrel at the shoulder portion thereof and insert the mixing bead 10 therein before assembling the glass bank around the mandrel. The shell sections 18 and 24) are made of a suitable metal so that they can be dissolved after the pipette has been completed by means of a suitable acid such as nitric or hydrochloric acid. The mixing bead 10, however, should be made of glass or other material which is unaffected by the acid.

shape to provide a well portion having a flat base and the desired diameter when the glass blank is shrunk therearound. The ring is assembled around the mandrel immediately adjacent the shell section 20 and surrounds the mandrel portion 16' of reduced diameter.

In forming the pipette vacuum is drawn from the right hand end of the glass blank as indicated by arrow 24.

Simultaneously, heat is applied to the right hand end of the glass blank a by means of the gas burner 26 so as to soften the glass and cause it to shrink inwardly around the mandrel due to the pressure ditferential. As indicated in the successive views, FIGS. 5, 6 and 7, the gas burner is shifted to the left causing the progressive shrinking of the glass blank around the mandrel and shell sections.

In forming the well and bulb portion of the pipette, I preferably proceed as follows: Just as the glass is softened adjacent the shell sections and ring 22 a sudden vacuum of short duration is drawn from the left hand of the blank as viewed in FIGS. 7 causing the blank to shrink in sharp conformity withthe shell sections and ring as shown.

Throughout the shrinking operation cooling fluid is preferably circulated through the mandrel.

It will be noted that in the drawings the bore of the 'aspirator portion of the pipette has been shown as of tailstock and headstock are separated so that the pipette 'may be removed therefrom and the mandrel and pipette are shifted longitudinally relative to each other to free the pipette from the mandrel. Nitric or hydrochloric acid is then inserted into the bulb of the pipette so as to dissolve the shell sections and metal ring and thereafter the interior of the pipette is flushed and cleaned. The tip of the pipette is then finished in the usual manner and the head of the aspirating portion is cut and beveled as shown. Thereafter graduations or markings such as shown at 12 may be applied, the pipette is cleaned and sterilized and may be packaged in a suitable manner.

The pipette may be used in the usual manner by inserting the tube of the capillary in blood until it fills due to capillary action. The physician or technician will have no difliculty in determining that the capillary bore 8 has been properly filled to the base of the Well due to the flat configuration of the base and the freedom from stress and retracting eflect.

The procedure may then be continued in the usual manner. Thus, generally a flexible tube has been applied to the aspirating end of the pipette and the operator places the end of the tube in his mouth and immerses the tip of the pipette in a body of diluent. He draws the diluent 4 into the pipette and simultaneously will draw the column of blood within the capillary into the mixing chamber. A precise ratio can be obtained by drawing'the diluent inwardly until the mixture. reaches the level of the mark ing 12. The zone of the pipette between the enlarged bulb and the marking 12 on the aspirating tube is likewise free from stresses and refracting etfect due to the one piece construction of the pipette. Accordingly, the operator has no difliculty'in establishing the proper dilution ratio.

It Will thus be seen that I have provided an improved pipette having a Window portion at the zone of connection between the capillary and bulb whereby the level of the fluids drawn into the pipette can be readily determined withoutdistortion or refraction. Modifications may be made in the illustrated and described embodiment of the invention without departingfrom the invention as set forth in the accompanying claims.1

I claim:

1. A pipette comprising a tubular member formed of one piece of glass and having a capillary tube portion adjacent one end, an enlarged bulb' portion communicating therewith and providing a mixing chamber and a Well portion disposed between the'capillary portion and the enlarged bulb portion, said well portion having a cylindrical side Wall and a fiat base disposed at right angles to the side wall at the end adjacent the capillary tube which defines the end of the bore in the capillary tube and the glass in the well portion and the adjacent capillary and bulb portions being substantially free from internal stresses and light-ray distortion characteristics. 1 V

2. A pipette comprising a tubular member formed of one piece of glass and'having a capillary. tube portion adjacent one end, an aspirating tube portion adjacent the other end, an enlarged bulb portion providing a mixing chamber communicatingdirectly with the aspirating portion and a well portion disposed between and communicating with the capillary and enlarged bulb portions, said well portion having a cylindrical sidewall and a flat base disposed substantially at right angles to the axis of the pipette defining the upper end of the borelof the capillary portion, and the glass in said well portion, bulb portion and adjacent zones of the capillary and aspirating portions being substantially free from internl stresses and from light distortion characteristics.

References Cited by theExaminer 7 UNITED STATES PATENTS 1,678,540 7/28 Trenner 73-425.4 2,104,325 1/38 Jul-fa 73 -425.4 X 2,735,230 V 2/56 I Morrell --23 3,091,104 5/63 Morrell 6555 RICHARD C. QUEISSER, Primary Examiner.

JOSEPH P. STRIZAK, Examiner. Q 

1. A PIPETTE COMPRISING A TUBULAR MEMBER FORMED OF ONE PIECE OF GLASS AND HAVING A CAPILLARY TUBE PORTION ADJACENT ONE END, AN ENLARGED BULB PORTION COMMUNICATING THEREWITH AND PROVIDING A MIXING CHAMBER AND A WELL PORTION DISPOSED BETWEEN THE CAPILLARY PORTION AND THE ENLARGED BULB PORTION, SAID WELL PORTION HAVING A CYLINDRICAL SIDE WALL AND A FLAT BASE DISPOSED AT RIGHT ANGLES TO THE SIDE WALL AT THE END ADJACENT THE CAPILLARY TUBE WHICH DEFINES THE END OF THE BORE IN T HE CAPILLARY TUBE AND THE GLASS IN THE WELL PORTION AND THE ADJACENT CAPILLARY AND BULB PORTIONS BEING SUBSTANTIALLY FREE FROM INTERNAL STRESSES AND LIGHT-RAY DISTORTION CHRACTERISTICS. 